The primary goal of this research is to develop mass spectrometric instrumentation and analytical procedures which will provide a rapid and practical means for elucidating the structures of high molecular weight biomolecules. Experiments performed by the author during the last year have demonstrated the technical feasibility of a new analytical instrument which may provide a means for accomplishing this goal. The instrument is called a "tandem quadrupole-Fourier transform mass spectrometer." Ions made in the source of a commercial quadrupole mass spectrometer are extracted and focused into a beam by quadrupole rods. The ion beam is then injected axially into a superconducting electromagnet where the ions are stored in an analyzer cell and detected using the methods of Fourier transform mass spectrometry. The instrument requested in this proposal would seek to combine the highly developed chromatographic and sample ionization features of a quadrupole mass spectrometer with the ultra-high mass resolution and high sensitivity features of Fourier transform detection. Analytical applications of the new spectrometer will be directed towards elucidating the structures of high molecular weight molecules. In particular, laser photodissociation will be investigated as a means for fragmenting ions in a controlled and sequential manner while they are stored in the analyzer cell of the FTMS instrument. Recent experiments performed in our laboratory with a conventional Fourier transform mass spectrometer fitted with a direct insertion probe have shown that di- and tripeptides can be photofragmented efficiently with one pulse from an excimer UV laser. Once better sample volatilization methods, such as fast atom bombardment and thermospray liquid chromatography, are mated with this capability, it will be possible to study the photofragmentation pathways of higher molecular weight polypeptides, saccharides and nucleotides.